Known vehicle systems use hybrid powertrain architectures to generate tractive torque using plural torque-generative devices including internal combustion engines and one or more non-hydrocarbon-fueled torque machines, which may include electric machines that transform electric power to mechanical torque. Hybrid powertrain architectures may be configured to transfer tractive torque to an output member through a transmission device. Hybrid powertrain architectures can include series-hybrid configurations, parallel-hybrid configurations, and compound-split hybrid configurations. Electric machines operative as motors and generators can be controlled to generate torque inputs to the transmission independently of a torque input from the internal combustion engine. The electric machines may react and transform vehicle kinetic energy transmitted through the vehicle driveline to electrical energy that is storable in an electrical energy storage device employing regenerative braking and other methods. A control system monitors various inputs from the vehicle and the operator and provides operational control of the powertrain, including controlling transmission operating range state and gear shifting, controlling operation of the engine and the torque machines, and regulating the electrical power interchange among the electrical energy storage device and the electric machines to manage torque and rotational speed outputs of the transmission.
Known control systems control operation of an engine to one of an engine-on mode and an engine-off mode, which may include a fuel cutoff mode. Known control systems control operation of a hybrid powertrain system to generate tractive torque, including tractive torque for launching a vehicle from a zero-speed or near zero-speed condition in response to an operator request for output torque.
Vehicles equipped with hybrid powertrain systems and extended-range electric vehicle powertrain systems may operate using battery charge-depletion control schemes or battery charge-sustaining control schemes. All energy for propulsion including energy for battery charging originates from on-board fuel in a vehicle that employs a battery charge-sustaining control scheme. Thus, a vehicle employing a battery charge-sustaining control scheme may command operation of the engine under conditions when an operator is expecting vehicle operation in an electric-only mode, such as during a low speed launch. However, avoiding operation of the engine in specific circumstances may negatively affect overall fuel economy due to a need to provide battery charging under less-optimal conditions. Vehicle and powertrain control schemes are expected to provide consistent vehicle operation during maneuvers, e.g., launches, and consider vehicle metrics such as fuel economy.